Filly putting her butt to me every time?

Make leading fun! She might be trying to lead because she associates leading with work or being take away from her buddies or from food. So to fix this, catch her like you normally do, but ten do something fun or nice, like continuing to let her eat, giving her treats, taking her out to graze or with her buddies. Anything fun and interesting to her. Eventually, she should be more willing to lead.